The present invention relates to a main helicopter drive. Helicopter drives are known to present an input connected to the drive shaft and an output connected to the main shaft powering the rotor. Drives of the aforementioned type generally present at least one more output connected to a duty or countershaft the function of which is to power the utilities and control systems on the helicopter, such as the hydraulic and electric systems.
One of the problems posed by drives of the aforementioned type is how to keep the countershaft running with the engine on and the rotor off. On known types of drives, this problem is generally solved using two coaxial tubular bodies, the first of which is fitted inside the second and angularly integral with the main shaft. The said second tubular body is designed to transmit the drive torque to the countershaft, on one side, by means of a gear train, and to the inner tubular body, on the other, by means of a freewheel designed to enable autorotation of the rotor and comprising internal locking members which may be controlled in such a manner as to impair operation, i.e. transmission of the drive torque to the main shaft. In addition to involving relatively complicated, highcost design, freewheels of the aforementioned type afford little reliability and constitute a critical part of the drive as a whole.